Ki-67 labeling index as an independent prognostic factor in human esophageal squamous cell carcinoma

Abstract

Although the Ki-67 labeling index (LI) is frequently used to determine the proliferative activity of malignant tumors, no consensus has been reached about its clinicopathological significance in esophageal squamous cell carcinoma (ESCC). In this study, we sought to determine an adequate Ki-67 LI cutoff value and investigated its prognostic significance in ESCC. The Ki-67 LI was calculated by immunohistochemistry for 49 primary tumor samples obtained from ESCC patients who had undergone curative esophagectomy, and the correlations between the Ki-67 LI and various clinicopathological features or prognosis were analyzed. The Ki-67 LI of the tumors ranged from 5.3 to 55.9 %. The mean Ki-67 LI increased from 27.4 % in pN0 tumors to 40.3 % in pN3 tumors. The 5-year survival rate decreased as the Ki-67 LI increased. When the patients were divided into two groups using an Ki-67 LI cutoff value of 35 %, the 5-year survival rate of the patients with Ki-67 LI of <35 % was 82.9 %, which was significantly higher than that of the patients with Ki-67 LI of ≥35 % (35.7 %). The percentage of pN-positive tumors was significantly higher among the patients with Ki-67 LI of ≥35 % (85.7 %) than in patients with Ki-67 LI of <35 (48.6 %). Multivariate analysis demonstrated that pT and pN categories and the Ki-67 LI were independent prognostic factors. These observations indicate that the Ki-67 LI is correlated with lymph node metastasis and can be used as an independent prognostic factor for ESCC patients by selecting an adequate cutoff value.